Steer-by-wire steering system and method for operating a steer-by-wire steering system

Patent metadata

Field	Value
Publication number	US-11878746-B2
Application number	US-202017120488-A
Country	US
Kind code	B2
Filing date	Dec 14, 2020
Priority date	Dec 12, 2019
Publication date	Jan 23, 2024
Grant date	Jan 23, 2024

Abstract

A steer-by-wire steering system for a vehicle is provided that includes a steering wheel actuator for moving and detecting movements of a steering wheel of the vehicle. The steering wheel actuator includes a steering wheel electric motor. The steer-by-wire steering system further includes an axle actuator for moving and detecting movements of wheels of an axle of the vehicle. The axle actuator includes an axle electric motor and an axle control unit. The steer-by-wire steering system an equivalent circuit, which measures a current induced by the steering wheel electric motor and provides the axle control unit with at least one measurement value depending on the induced current for controlling the axle electric motor.

First claim

The invention claimed is:

1. A steer-by-wire steering system for a vehicle comprising:
a steering wheel actuator ( 12 ) for moving and detecting movements of a steering wheel ( 16 ) of the vehicle, which has a steering wheel electric motor ( 20 ) connected to the steering wheel ( 16 ) of the vehicle,
an axle actuator ( 14 ) for moving and detecting movements of wheels of an axle of the vehicle, which comprises an axle electric motor ( 32 ) and an axle control unit ( 30 ) and which is connected to the axle of the vehicle, and
an equivalent circuit ( 36 ) comprised of a logic circuit to measure a current (U, V, W) induced by the steering wheel electric motor ( 20 ) and to provide the axle control unit ( 30 ) with at least one measurement value depending on the induced current (U, V, W) for controlling the axle electric motor ( 32 ).

2. The steer-by-wire steering system as claimed in claim 1 , wherein the equivalent circuit ( 36 ) has at least one current sensor ( 26 ) which is assigned to a phase of the steering wheel electric motor ( 20 ), wherein the equivalent circuit ( 36 ) has as many current sensors ( 26 ) as the steering wheel electric motor ( 20 ) has phases.

3. The steer-by-wire steering system as claimed in claim 1 , wherein as many measurement values are provided as the steering wheel electric motor ( 20 ) has phases.

4. The steer-by-wire steering system as claimed in claim 1 , wherein the axle control unit ( 30 ) is set up to record the measurement value and to control the axle electric motor ( 32 ) on the basis of the measurement value, wherein the axle control unit ( 30 ) is set up to determine the position of the steering wheel and/or a relative steering angle (φ) on the basis of the at least one measurement value.

5. The steer-by-wire steering system as claimed in claim 1 , wherein the equivalent circuit ( 36 ) has at least one branch that has a comparator ( 38 a , 38 b , 38 c ) and a switching element ( 40 a , 40 b , 40 c ), comprised of a transistor, wherein the comparator ( 38 a , 38 b , 38 c ) is connected to at least one current sensor ( 26 ) and is designed to actuate the switching element ( 40 a , 40 b , 40 c ) when the current (U, V, W) measured by the current sensor ( 26 ) exceeds a predetermined threshold value (S).

6. The steer-by-wire steering system as claimed in claim 1 , wherein at least one branch of the equivalent circuit ( 36 ) has a capacitor ( 42 a , 42 b , 42 c ), the voltage of which represents the measurement value.

7. The steer-by-wire steering system as claimed in claim 5 , wherein the equivalent circuit ( 36 ) has a voltage source ( 43 ) which is connected to the capacitor ( 42 a , 42 b , 42 c ) via the switching element ( 40 a , 40 b , 40 c ) when the switching element ( 40 a , 40 b , 40 c ) is actuated.

8. The steer-by-wire steering system as claimed in claim 5 , wherein the switching element ( 40 a , 40 b , 40 c ), is set up to discharge the capacitor ( 42 a , 42 b , 42 c ) if the current (U, V, W) measured by the current sensor ( 26 ) is below a predetermined threshold value (S).

9. The steer-by-wire steering system as claimed in claim 5 , wherein the equivalent circuit ( 36 ) has several branches, including a branch for each phase of the steering wheel electric motor ( 20 ), wherein each branch contains a logic block ( 44 a , 44 b , 44 c ) connected to the comparator ( 38 a , 38 b , 38 c ) of the branch and the comparators ( 38 a , 38 b , 38 c ) of another branch, wherein the logic block ( 44 a , 44 b , 44 c ) is set up to discharge the capacitor ( 42 a , 42 b , 42 c ) when the measured current (U, V, W) of the at least one other branch exceeds the threshold value (S).

10. The steer-by-wire steering system as claimed in claim 1 , wherein the steering wheel actuator ( 12 ) has a steering wheel control unit ( 18 ) which is connected to the axle control unit ( 30 ) for data exchange.

11. A method for operating a steer-by-wire steering system ( 10 ), which has a steering wheel actuator ( 12 ) with a steering wheel electric motor ( 20 ) and a steering wheel control unit ( 18 ), an axle actuator ( 14 ) with an axle electric motor ( 32 ) and an axle control unit ( 30 ) and a logic circuit ( 36 ), wherein the method includes the following steps:
checking whether there is a malfunction of the steering wheel control unit ( 18 ) by the axle control unit ( 30 );
measuring the current (U, V, W) induced by the steering wheel electric motor ( 20 ) by the logic circuit ( 36 ) and providing a measurement value depending on the induced current (U, V, W);
obtaining at least one measurement value from the logic circuit ( 36 ) by the axle control unit ( 30 ); and
controlling the steering movement of the axle by the axle control unit ( 30 ) by means of the axle electric motor ( 32 ) depending on the at least one measurement value obtained if there is a malfunction.

12. The method as claimed in claim 11 , wherein a measurement value is provided for each phase of the steering wheel electric motor ( 20 ).

13. The method as claimed in claim 11 , wherein each phase is assigned a capacitor ( 42 a , 42 b , 42 c ), wherein the capacitor ( 42 a , 42 b , 42 c ) is linearly charged, when the current (U, V, W) of the phase exceeds a predetermined threshold value (S).

14. The method as claimed in claim 11 , wherein the at least one measurement value is a voltage of a corresponding capacitor ( 42 a , 42 b , 42 c ).

15. The method as claimed in claim 11 , wherein the axle control unit ( 30 ) determines the position of the steering wheel and/or a relative steering angle φ using the at least one measurement value.

Assignees

• Zf Automotive Germany Gmbh

Inventors

• Bergmann Philipp

Classifications

• B62D5/046 Primary

  Controlling the motor · CPC title

• B62D1/04

  Hand wheels · CPC title

• B62D5/003

  Backup systems, e.g. for manual steering (B62D5/30 takes precedence) · CPC title

• B62D5/0481

  monitoring the steering system, e.g. failures · CPC title

• B62D5/0463 Primary

  calculating assisting torque from the motor based on driver input · CPC title